Differentially entangled nonwoven fabric for use as wipes

ABSTRACT

The invention is directed to a hydroentangled nonwoven wipe, the outer surface of which exhibits highly entangled fibers whereas the inner layer exhibits lightly entangled fibers. In particular, the present invention contemplates that a fabric is formed from a fibrous batt that is subjected to fluidic energy, preferably hydraulic energy, applied to one or both faces of a fibrous batt. The hydraulic energy is moderated against the basis weight of the fibrous batt to achieve the degree of surface entanglement desired. Wipes formed in accordance with the present invention exhibit a sufficient degree of strength, softness and non-linting performance, while providing the necessary resistance to tearing and abrasion, to facilitate use in a wide variety of applications utilizing wipes, such as graphic arts and lithography.

TECHNICAL FIELD

[0001] The invention disclosed herein is directed to wipes, preferablywipes for use in graphic arts or lithography, made from a hydroentanglednonwoven fabric, whereby the outer surface fibers of a single fibrousbatt are highly hydroentangled and the inner fibers of the singlefibrous batt are lightly entangled, the resulting fabric thus exhibits alow linting, lofty structure, and favorable tactile and ductile softnesswhile obtaining sufficient physical strength.

BACKGROUND OF THE INVENTION

[0002] The use of natural fiber materials in industrial applications hasbeen found to be highly advantageous in situations where a non-linting,absorbent pad or wiper is required. A material that has been employed insuch applications is found in the Webril material from the KendallCompany of Massachusetts. The Webril material is a compressed,mercerized cotton fibrous batt. The mercerization process involves theswelling of the natural cotton's ribbon like profile into anapproximately round profile of larger diameter. Typically, causticwashes are utilized while the cotton batt is under tension to induce theswelling of the cotton fiber. Because of the use of a caustic solution,it is necessary to subsequently treat the cotton material with an acidicsolution so as to neutralize the material and render it useable. Anumber of complicated steps are required to successfully perform theprocess, with a significant amount of environmentally harmful effluentbeing produced.

[0003] In the interest of forming natural fiber nonwoven pads or wiperswithout the by-products of mercerization, the application of a resinbinder in conjunction with hydroentanglement was explored as evidencedby U.S. Pat. Nos. 2,862,251, 3,033,721, 3,769,659, and 3,931,436 toKalwaites et al., and U.S. Pat. Nos. 3,081,515 and 3,025,585 to Griswoldet al, the disclosures of which are herein incorporated by reference.The application of resin binder was found to have a deleterious effecton the softness of the corresponding nonwoven fabric.

[0004] The findings by Evans, U.S. Pat. No. 3,485,706, the disclosure ofwhich is herein incorporated by reference, suggested that the impedanceof energetic water streams on a fibrous batt could produce a nonwovenfabric by the entanglement of those fibers with one another through thedepth of the fibrous batt, thus obviating the need for a resin binder.However, the action of the water streams upon the fibrous batt and theaction of entangling the fibers result in a fabric having significantlydecreased bulk, and correspondingly decreased tactile and ductilesoftness.

[0005] Various attempts have been made in order to obtain a durablenatural fiber nonwoven fabric while maintaining sufficient strength andsoftness. In U.S. Pat. No. 5,849,647 to Neveu, the disclosure of whichis herein incorporated by reference, a hydrophilic cotton stratifiedstructure is formed by interceding an air-randomized core in between twopreviously formed, highly fiber oriented carded layers. The stratifiedlayers are subsequently treated with a soda liquor which is then boiledoff to render an integrated structure. While a cotton structureperformed by the manner described can render an ultimate material thatis low linting, the material must undergo substantial processing in theforming of separate and distinct layers and the juxtaposition of thoselayers during the caustic integration step. U.S. Pat. No. 4,647,490 toBailey et al., the disclosure of which is herein incorporated byreference, formed an apertured, cotton fiber nonwoven material byhydroentanglement induced by oscillating water streams. In the Baileyprocess, the fibers of the fibrous batt are washed down and through thefibrous batt in order to entangle the fibers and form apertures in thefabric. U.S. Pat. No. 4,426,417 to Meitner et al., the disclosure ofwhich is herein incorporated by reference, incorporated the use ofthermoplastic meltblown during the formation of a fibrous batt as ameans for attaining the loft for absorbency and maintain sufficientphysical strength by bonding the fibers together. As the nature of theMeitner process is based upon the total and effective binding of thefibers to the thermoplastic meltblown there are potential issues withunbound or loosely bound fibers being disengaged from the meltblown.

[0006] Given the prior art attempt to form a nonlinting, soft and yetstrong absorbent materials, there remains a need for a nonwoven fabricexhibiting these characteristics and yet is formed in an expeditious anduncomplicated manner.

[0007] A method for forming a suitable nonwoven fabric meeting theaforementioned requirements has been identified in the application offluidic energy such that a single fibrous batt is imparted with a highlyentangled surface of outer fibers while retaining the loft andabsorbency of a lightly entangled central layer of core fibers.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to a method of forming anonwoven fabric, the outer surface of which exhibits highly entangledfibers whereas the inner layer exhibits lightly entangled fibers. Inparticular, the present invention contemplates that a fabric is formedfrom a fibrous batt that is subjected to fluidic energy, preferablyhydraulic energy, applied to one or both faces of a fibrous batt. Thehydraulic energy is moderated against the basis weight of the fibrousbatt to achieve the degree of surface entanglement desired.

[0009] In accordance with the present invention, a method of making anonwoven fabric embodying the present invention includes the steps ofproviding a fibrous batt comprising a fibrous matrix. While use ofnatural fibers is common, the fibrous matrix may comprise syntheticfibers or blends of natural and synthetic fibers. The synthetic fibersare chosen from the group consisting of viscose cellulose,polyacrylates, polyolefins, polyamides, polyesters and combinationsthereof. Further, the synthetic fibers may comprise homogeneous,bicomponent and/or multi-component profiles, and the blends thereof.

[0010] In a particularly preferred form, the fibrous batt is carded andcross-lapped to form a fibrous batt. The fibrous batt is thencontinuously indexed through a station composed of a rotary foraminoussurface and a fluidic manifold. Fluid streams from the fluidic manifoldimpinge upon the fibrous batt at a controlled energy level so as tointegrate a portion of the overall fibrous content. The energy level iscontrolled such that the energy is sufficient to induce high levels ofentanglement in the surface fibers, but has insufficient transmittedenergy to induce high levels of entanglement of the inner fibers. Aplurality of such stations can be employed whereby fluid streams are atthe same or differing energy levels, impinging one or alternately bothsurfaces of the fibrous batt. The resulting differentially entanglednonwoven web exhibits a highly entangled fibrous outer surface and alightly entangled fibrous core.

[0011] Subsequent to hydroentanglement, the present method furthercontemplates the provision of a three-dimensional image transfer devicehaving a movable imaging surface. Such three-dimensional image transferdevices are disclosed in U.S. Pat. No. 5,098,764, the disclosure ofwhich is herein incorporated by reference. In a typical configuration,the image transfer device may comprise a drum-like apparatus that isrotatable with respect to one or more hydroentangling manifolds.

[0012] It is within the purview of this invention that tension controlmeans can be employed to further enhance the physical performance of theresulting lofty material.

[0013] A further aspect of the present invention is directed to a methodof forming a nonwoven fabric which exhibits a sufficient degree ofsoftness and nonlinting performance, while providing the necessaryresistance to tearing and abrasion, to facilitate use in a wide varietyof applications. The fabric exhibits a high degree of loft andabsorbency, thus permitting its use in those applications in which thefabric is applied as a cleaning wipe. Further, the material exhibitspleasant aesthetics, thus lending itself to application in medicalapplications.

[0014] A method of making the present durable nonwoven fabric comprisesthe steps of providing a fibrous matrix or batt, which is subjected tocontrolled levels of hydraulic energy. A homogeneous cotton fibrous batthas been found to desirably yield a fabric with soft hand and goodabsorbency. The fibrous batt is formed into a differentially entanglednonwoven fabric by the application of sufficient energy to entangle onlythe outer layers of the fibrous batt. Subsequently, the fabric can bepassed over an image transfer device defined by three-dimensionalelements against which the differentially entangled nonwoven fabric isforced during further application of further energy, whereby the fibrousconstituents of the web are imaged and patterned by movement intoregions between the three-dimensional elements of the transfer device.

[0015] It is within the purview of the present invention that physicalproperty altering chemistries can be incorporated into the resultingdifferentially entangled fabric. Such chemistries include for exampleantimicrobial and antistatic agents that can be durably applied to theconstituent fibers of the fibrous batt, to the fibrous batt duringmanufacture, and/or to the resulting fabric.

[0016] Other features and advantages of the present invention willbecome readily apparent from the following detailed description, theaccompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a diagrammatic view of an apparatus for manufacturing adifferentially entangled nonwoven fabric, embodying the principles ofthe present invention; and

[0018]FIG. 2 is a diagrammatic view of five consecutive entanglingsections and an image transfer station.

DETAILED DESCRIPTION

[0019] While the present invention is susceptible of embodiment invarious forms, there is shown in the drawings and will hereinafter bedescribed a presently preferred embodiment of the invention, with theunderstanding that the present disclosure is to be considered as anexemplification of the invention, and is not intended to limit theinvention to the specific embodiment illustrated.

[0020] The present invention is directed to a method of forming nonwovenfabrics by hydroentanglement, wherein the outer surface of the fabric issubstantially more entangled than the core layer. Hydroentanglement bythis method is controlled by the application of fluidic energy such thatthe energy imparted into fibers of the fabric is sufficient to highlyentangle only the outer fibers. The inner fibers are lightly entangledsuch that the overall structure is resistant to separation of thelayers, yet retain much of the loftiness or bulk of the fibrous corelayer that is responsible for tactile and ductile softness as well asabsorbency. By advancing the fibrous batt with a relatively low tensionthrough one or more entanglement stations, differential fiberentanglement is achieved, with the physical properties, both aestheticand mechanical, of the resultant fabric being desirably achieved.

[0021] In accordance with a further aspect of the present invention, anonwoven fabric for application as a wipe can be produced such that thelevel of surface entanglement can be controlled resulting in surfacelayers that are extremely resistant to Tinting while the fabric retainssome loft of the fibrous inner layer. A material of this nature is foundto have use in the graphic arts and lithography as it can be employed asa non-abrasive, drapeable, absorbent wiper. Excessive linting from thewipe would be detrimental to the application, so increasing the level ofentanglement of the surface fibers should act to decrease Tinting fromthe highly entangled surface layer, which should act as a barrier toloss of fibers or particulates form the lightly entangled core. Thelevel of entanglement energy can be continuously varied to modify thephysical properties of the wipe material to meet the requiredperformance. It is within the scope of the present invention to controlthe level of entanglement in the resulting fabric to obtain materialswith varying degrees of loft, absorbency, strength, and lintingperformance.

[0022] Nonwoven fabrics are frequently produced using staple lengthfibers, the fabric typically has a degree of exposed surface fibers thatwill lint if not sufficiently retained into the structure of the fabric.The present invention provides a finished fabric that can be cut,processed or treated, and packaged for retail sale. The cost associatedwith forming and finishing steps can be desirably reduced.

[0023] With reference to FIG. 2, therein is illustrated an apparatus forpracticing the present method for forming a nonwoven fabric. The fabricis formed from a fibrous batt that typically comprises natural fibers,but may comprise synthetic staple fibers and natural/synthetic fiberblends. The fibrous batt is preferably carded and cross-lapped to form afibrous batt, designated P. In a current embodiment, the fibrous battcomprises 100% cross-lap fibers, that is, all of the fibers of the webhave been formed by cross-lapping a carded web so that the fibers areoriented at an angle relative to the machine direction of the resultantweb. In this current embodiment, the fibrous batt has a draft ratio ofapproximately 2.8 to 1. U.S. Pat. No. 5,475,903, the disclosure of whichis herein incorporated by reference, illustrates a web draftingapparatus.

[0024]FIG. 2 illustrates a hydroentangling apparatus for formingnonwoven fabrics in accordance with the present invention. The apparatusincludes a foraminous forming surface in the form of belt 02 upon whichthe fibrous batt P is positioned for pre-entangling by entanglingmanifold 01 into a wetted, lightly entangled fibrous web P′.Pre-entangling of the fibrous web is subsequently effected by movementof the web P′ sequentially over a drum 10 having a foraminous formingsurface, with entangling manifold 12 effecting entanglement of the web.Further entanglement of the web may be effected on the foraminousforming surface of a drum 20 by entanglement manifold 22, with the websubsequently passed over successive foraminous drums 30, 40 and 50, forsuccessive entangling treatment by entangling manifolds 32, 42 and 51.The total, optimal energy input to the fibrous batt to give the desiredlevel of surface entanglement is in the range of about 0.040 to 0.060hp-hr/lb.

[0025] The entangling apparatus of FIG. 2 may further include an imagingand patterning drum 18 comprising a three-dimensional image transferdevice for effecting imaging and patterning of the now-entangledprecursor web. The image transfer device includes a moveable imagingsurface which moves relative to a plurality of entangling manifolds 61,62, 63 and 64, which act in cooperation with three-dimensional elementsdefined by the imaging surface of the image transfer device to effectimaging and patterning of the fabric being formed. The total energyapplied to the fibrous batt of the imaging manifolds is adjusted tomaintain the energy input in the range of about 0.040 to 0.060 hp-hr/lb.

[0026] The present invention contemplates that the fibrous web P′ beadvanced onto the moveable imaging surface of the image transfer deviceat a rate which is substantially equal to the rate of movement of theimaging surface. A J-box or scray can be employed for supporting theprecursor web P′ as it is advanced onto the image transfer device tothereby minimize tension within the fibrous web. By controlling the rateof advancement of the fibrous batt P and the web P′ through the processso as to minimize, or substantially eliminate, tension within the web,differential hydroentanglement of the fibrous web is desirably effected.

[0027] Manufacture of a durable nonwoven fabric embodying the principlesof the present invention is initiated by providing the precursornonwoven web preferably in the form of a natural and/or syntheticfibers, most preferably a cotton or cotton blend, which desirablyprovides good tactile and ductile softness and absorbency. Duringdevelopment, it was ascertained that fabric weights on the order ofabout 1 to 8 ounces per square yard, with the range of 2 to 5 ounces persquare yard being most preferred, provided the best combination of loft,softness, drapeability, absorbency, and durability.

EXAMPLES Example 1

[0028] Using a forming apparatus as illustrated in FIG. 1, a nonwovenfabric was made in accordance with the present invention by providing afibrous batt comprising 100 weight percent cotton fiber. The fibrousbatt had a basis weight of 3.4 ounces per square yard (plus or minus7%). The fibrous web was 100% carded and cross-lapped, with a draftratio of 2.8 to 1.

[0029] The fabric comprised 100 weight percent cotton as available fromBarnhardt Manufacturing Company under code number RMC#2811. The fibrousbatt was entangled by a series of entangling manifold stations such asdiagrammatically illustrated in FIG. 1 and in greater detail in FIG. 2.FIG. 2 illustrates disposition of fibrous batt P on a foraminous formingsurface in the form of belt 02, with the batt acted upon by apre-entangling manifold 01 operating at 55 bar to form a wetted andlightly entangled fibrous web. The web then passes through a series ofentangling stations comprising drums having foraminous forming surfaces,for entangling by entangling manifolds, with the web thereafter directedabout the foraminous forming surface of a drum 10 for entangling byentanglement manifold 12 operating at 40 bar. The web is thereafterpassed over successive foraminous drums 20, 30, 40 and 50, withsuccessive entangling treatment by entangling manifolds 22, 32, 42 and51. In the present examples, each of the entangling manifolds included120 micron orifices spaced at 42.3 per inch, with manifolds 22, 32, 42and 51 successively operated at 55, 40, 55, and 0 bar, with a line speedof 45 meters per minute. The total energy input into the fibrous batt iscalculated to be 0.052 hp-hr/lb. A web having a trimmed width of 127inches was employed.

Comparative Example

[0030] The comparative example is selected from a commercially availableproduct in the form of Webril 100% Cotton Handi-Pad as available fromthe Kendall Company. This product is formed by compression formingcotton fiber during a mercerization process.

[0031] The accompanying Table 1 sets forth comparative test data for afabric made by the present invention compared against a commerciallyavailable mercerized cotton fabric. Testing was done in accordance withthe following test methods. Test Method Basis weight (ounces/yd² ASTMD3776 Bulk (inches) ASTM D5729 Tensiles MD and CD Grabs (lb/in) ASTMD5034 Elongation MD and CD Grabs (%) ASTM D5034

[0032] The physical test data for Example 1 and the Comparative Exampleare given in Table 1. The data in Table 1 show that the two materialshave similar basis weights, but the nonwoven fabric manufactured by thepresent invention has much greater tensile strength in both the machineand cross direction, 20 and 40 times greater, respectively, than that ofthe Comparative material. In addition, the tensile properties of Example1 are more uniform when comparing the machine direction to the crossdirection tensile and elongation properties.

[0033] From the foregoing, it will be observed that numerousmodifications and variations can be affected without departing from thetrue spirit and scope of the novel concept of the present invention. Itis to be understood that no limitation with respect to the specificembodiments illustrated herein is intended or should be inferred. Thedisclosure is intended to cover, by the appended claims, all suchmodifications as fall within the scope of the claims. TABLE 1Comparative Physical Property Units Example 1 Example Basis Weight osy3.4 3.2 Bulk inches 0.033 0.061 Grab Tensile - MD lb./in. 23.3 1.3 GrabTensile - CD lb./in. 23.3 0.5 Combined Grab Tensile/Basis Weight 13.70.6 Grab Elongation - MD % 32.9 35.4 Grab Elongation - CD % 76.1 118.7Combined Grab Elongation/Basis 32.1 48.2 Weight

What is claimed:
 1. A nonwoven wipe, comprising a single fibrous battwhereupon the single fibrous batt is entangled by the application ofhydraulic energy to form a nonwoven wipe, said nonwoven wipe having ahighly entangled outer surface region and a lightly entangled inner coreregion.
 2. A nonwoven wipe as in claim 1 wherein the fibrous battcomprises cotton.
 3. A nonwoven wipe as in claim 1 wherein the fibrousbatt comprises a blend of cotton and synthetic staple fibers.
 4. Anonwoven wipe as in claim 3 wherein the synthetic staple fibers areselected from the group consisting of viscose cellulose, polyacrylates,polyolefins, polyamides, polyesters and the combinations thereof.
 5. Anonwoven wipe as in claim 1 formed by the application of hydraulicenergy in the range of about 0.040 to 0.060 hp-hr/lb.
 6. A nonwoven wipeas in claim 1, wherein the fabric is imaged by the application ofhydraulic energy upon a three-dimensional image transfer device having amovable imaging surface.
 7. A nonwoven wipe as in claim 1, wherein thefabric further comprises one or more physical performance enhancingchemistries.